This invention relates to a motor driving circuit and, more particularly, to a motor driving circuit capable of driving a motor with a single common circuit, e.g., a single integrated circuit, regardless of whether the motor to be driven is a brush motor or a brushless motor.
Speed and rotation direction controls are necessary for motors of certain types such as a capstan motor in a DAT (digital audio tape recorder) to cope with modes of operation such as normal speed playback and double speed playback or fast forward rotation and fast reverse rotation. Speed control is necessary for a drum motor and a reel motor to cope with normal speed playback, double speed playback and high speed search.
As these motors, a brush motor or a brushless motor is used depending upon the purpose of the motor. Since a brush motor and a brushless motor are driven by different methods of driving, a drive circuit proper to a motor to be used must be designed after the type of the motor has been determined.
In a case where a brush motor is used, a drive signal of characteristics shown in FIG. 2 is used. In this drive signal, the rotation direction is determined by polarity of voltage and the speed is determined by the absolute value of voltage. In a case where a brushless motor is used, a drive signal of characteristics shown in FIG. 3 is used. In this drive signal, the speed is determined by the absolute value of voltage and the rotation direction is determined by a separate rotation direction command.
In designing a motor driving circuit, according to the conventional method, whether the motor to be used is a brush motor or a brushless motor is first determined and a motor driving circuit producing a drive signal as shown in FIG. 2 or FIG. 3 is designed depending upon the type of the motor to be used. It is a recent tendency to design such motor driving circuit with an integrated circuit and, in this case, an integrated circuit adapted to the type of the motor to be used must be selected or an external circuit must be additionally provided.
Thus, the necessity for selecting a driving circuit depending upon the type of the motor to be used prevents application of an integrated circuit to general uses.
It is, therefore, an object of the invention to provide a motor driving circuit capable of adapting both to a brush motor and a brushless motor whereby scope of application of an integrated circuit employing this motor driving circuit can be broadened.